This application relates generally to the field of hydraulic compactors and more particularly relates to such compactors having reversible rotary pumps for the distribution of hydraulic fluid, the pumps changing the direction of rotation (clockwise/counter-clockwise) to change the direction of movement (extension/retraction) of the piston of a hydraulic compacting cylinder.
Hydraulic compacting systems, i.e., equipment that compresses material, often consisting of a plurality of objects (e.g., trash, cardboard boxes, etc.), into a compacted bundle for easier handling, transport, storage, etc., are well known. In basic form, a hydraulic system operates a cylinder having a reciprocating piston that extends to compress the material and retracts to release the material, the compaction stroke being a high-pressure stroke and the retraction stroke being a low-pressure stroke. Many hydraulic compacting systems utilize a rotary hydraulic pump, wherein rotation in one direction initiates the compaction stroke and rotation in the opposite direction initiates the retraction stroke.
In many compacting situations, when the piston is fully extended in the compaction stroke, the compacted material retains an elastic or residual load that pushes against the piston in the retraction direction. For systems having rotary hydraulic pumps, the force from this residual load can damage the rotary pump, since in operation the pump must reverse the direction of rotation to change the flow direction of the hydraulic fluid. It is an object of this invention to provide a relief system that prevents damage to the rotary pump from the stresses imparted by the residual load of the compacted material.